Double revolving looper for sewing machines

ABSTRACT

Double revolving loopers for sewing machines whose bobbin cage holder flange is mounted on a looper track on the hub side of and integral with the looper body, is covered and adjustably retained on the opening side, to provide for required small tolerance, by a retaining ring with a substantially round cross section and bearing on an inclined surface of the looper body.

United States Patent Barthel et a1. 1 1 Aug. 5, 1975 [54] DOUBLE REVOLVING LOOPER FOR 3,232,258 2/1966 Gegauf, Jr. 112/228 SEWING MACHINES [75] Inventors: Werner Barthel, Dresden; Walter FOREIGN PATENTS OR APPLICATIONS Schlawitz, Meissen, both of 236,843 7/1925 United Kingdom 112/228 11,034 7/1895 United Kingdom... 1 12/228 Germany 923,266 7/1947 France 112/228 [73] Assignee: VEB Nahmaschinenwerk Wittenberge, Wittenberge, Germany Primary Examiner-Werner H. Schroeder 122] filed: 121 1973 Attorney, Agent, or FirmNo1te and Nolte [21] Appl. No.: 415,261

[30] Foreign Application Priority Data [57] ABSTRACT Jan. 22, 1973 Germany 0516835 Double revolving loopers for Sewing machines Whose 52 US. Cl. 112/228 bbbm Cage hddef flarge mounted. track on the hub s1de of and integral w1th the looper [51] Int. Cl.- D05B 57/14 bod is Covered and adhstabl retained on the 0 cm [58] Field of Search 112/181, 183,184,189, J y p mg side, to provide for requlred small tolerance, by a 112/228, 230

retalmng rmg with a substantlally round cross sect1on 56] References Cited and bearing on an inclmed surface of the looper body.

UNITED STATES PATENTS 8 Claims, 8 Drawing Figures 3.097.619 7/1963 Cerliani 112/228 PATENTEUAUB 5% I4 1/ IO FIG? DOUBLE REVOLVING LOOPER FOR SEWING MACHINES Known types of loopers have on the front, opened side of the looper body opposite the hub an integral rib which acts as an axial sliding bearing and which exerts under the looper point a sewing-related guiding function for the upper thread. Furthermore these loopers are provided with a cover ring, threaded for the assembly and disassembly of the stationary bobbin cage holder, and which ring provides an extension of the axial guiding function of the rib and covers thelooper track to a great extent.

It has been suggested to cover the looper track completely or partly with an elastically mounted sheet metal ring with a substantially rectangular cross section, in order to prevent jamming of the bobbin cage holder when thread pieces get into the looper track. Retention of such a cover ring is effected by connecting it via spring elements with the looper body to urge it toward bearing cams on the looper body.

In another known looper, a solution is provided which prevents blocking of the bobbin cage holder by thread pieces and dust. This is achieved in by retaining the cover ring on the looper by means of bolts arranged parallel to the looper axis, which bolts are secured on prestressed leaf springs connected rigidly with the looper. A thread which has got into the path of motion is to be eliminated during the yielding of the cover ring by a revolving slot provided between the looper body wall and the cover ring.

In order to maintain the bearing play, it is described elsewhere that such bolts have coil springs surrounding them, which bear, on the one hand, on the looper and, on the other hand, on the cover ring or bolt head. Furthermore, cover rings are known being elastically held in place by bayonet joints.

ln another known looper, the cover ring is held in the desired axial position relative to the looper body by adjustable screws and stops which protrude axially through the bearing surfaces of the cover ring or looper body.

In order to prevent the thread from getting into the looper track, it has also been suggested that a retaining ring covering the looper track on the opening side can yield elastically in the axial direction of the looper when the thread is in the way. Thisretaining ring is designed as an open profiled snap ring secured with one free end on the looper body, and which is held by an inner cone arranged on the looper body and widening in the direction of the bobbin cage holder.

All of the above solutions for the axial support of the bobbin cage holder in the looper body and for covering the looper track opening have several disadvantages.

Because of the fixed rib in the looper body, the bobbin cage holder can only be inserted in a certain position to the looper body, thus rendering the assembly difficult. The adaptation of the width of the guideway under the fixed rib to the position of the cover ring is very complicated from a manufacturing viewpoint. The rib cannot be too large or it will prevent assembly. Furthermore, interruptions in the formation of the rib, of varying length for different types of loopers, are necessary up to the cover ring which is missing, however, as a guide surface in the bearing. The unequal distribution of the mass by the form of the cover ring produces an imbalance which must be compensated in high-speed loopers by fly weights on the hub.

The bearing of the cover ring results in a weakening of the looper body wall, which increases the possibility of distortion in the heat treatment. The proper fit of the cover ring is determined by the exact position of its fastening screws in the looper body wall and of conically counter-sunk through-holes in the cover ring. Deviations from this position result in fluctuations in the bearing play, for which compensation must then be made by hand.

Furthermore, if the looper track or the bobbin cage holder flange are worn out, the entire looper must be replaced by a new one, though other parts, like the looper point or the needle guard on the bobbin cage holder are still usable. There is no possibility of readjusting the track play when the machine elements are worn out.

In the known solutions, the track play can be adjusted neither axially nor radially, nor in both directions, even during the assembly. All these nonadjustable loopers have thus the disadvantage that the play achieved in the pairing of bobbin cage holder and looper body during the assembly is at first kept constant and the low torque required for a good operation is established either only when the surface elevation is worn out or the low torque is achieved from the beginning by a large play resulting in non-uniform and relatively quick wear.

The invention is based on the problem of providing a looper of the above mentioned type which avoids the disadvantages of the known loopers and which has a means for adjusting and readjusting the track play between looper body and bobbin cage carrier in either or both the axial and radial direction.

The problem is solved according to the invention in by the provision of a retaining ring with a substantially round cross section, bearing outwardly due to its initial stress, on an inclined surface provided on the looper body, the ring covers the looper track and adjustable counterholding elements are provided on the opening side of the looper, to retain the ring in place and to permit the adjustment and readjustment of the track play.

The position of the retaining ring is determined on the opening side by these elements which are radially adjustable. I

The safe passage of the upper thread to the retaining ring under the looper point is effected by a small bend of a retaining ring end to the outside, which engages an oblong slot provided on the looper point and ensuring sufficient play in the axial direction.

The safe sliding of the upper thread from the retaining ring is ensured by the unbent end of this retaining ring in that it terminates in a point which is formed by the increase of the inside ring diameter at the outer ring edge.

The above mentioned adjustability of the retaining ring in the axial direction only results when the bobbin cage holder flange has a rectangular cross section, while with a bevel on the front side of the bobbin cage holder, flange both the axial and the radial play can be adjusted.

The invention makes it possible to adjust and readjust the play between the bobbin cage holder flange and the looper track in the assembly or if the track surfaces are worn-out with a reliable and constructionally simple design which substantially facilitates the assembly of the bobbin cage carrier. Beyond that small errors in the track geometry can be easily eliminated and the low torque necessary for improving the sewing can be achieved.

An embodiment of the invention is represented in the enclosed drawings and described more fully below.

FIG. 1 shows a complete double revolving double back stitch sewing machine looper in a perspective view.

FIG. 2 shows a bobbin cage carrier in a rear view.

FIG. 3 shows a bobbin cage carrier in a lateral view.

FIG. 4 shows a looper body with inserted retaining ring in a front view.

FIG. 5 shows a retaining ring in a top plan view.

FIG. 6 shows a part of the development of the looper body surface with looper point seen from the inside.

FIG. 7 shows a sectional partial view of the looper with retaining ring, threaded pin, as well as a bobbin cage carrier flange having a rectangular cross section.

FIG. 8 shows a sectional partial view according to FIG. 7 with reveled bobbin cage holder flange.

The double revolving sewing machine looper is composed, as known, of the looper body 1 secured on the looper shaft (not shown), the bobbin cage carrier 2 arranged in the looper body and the bobbin cage 3 received by the carrier 2. The bobbin cage carrier 2 has on its outer wall a bobbin cage holder flange 4 which is received by the looper track 5 of the inner wall 6 of the looper body.

Above the looper track 5 is arranged an inclined surface 7 which serves as a bearing surface for the retaining ring 8. This retaining ring 8 is so designed that one end 9 is bent and engages an oblong slot 10 of the looper point 11 (see FIG. 5 and FIG. 6) and that its initial stress urges it outwardly. The unbent end 15 of the retaining ring 8 terminates in a point.

Distributed over the circumference of the looper body wall above the inclined surface 7, three threaded pins, l2; l3; l4 effect the axial and radial locking of the retaining ring 8. Thus it is possible to adjust and readjust the axial play in bobbin cage holder 2 with a rectangular cross section of the bobbin cage holder flange 4 according to FIG. 7. The axial as well as the radial play between the bobbin cage holder 2 and the looper track 5 can be adjusted with a bevel of the bobbin cage holder flange 4 according to FIG. 8. This play can be regulated, if necessary by tightening or loosening the threaded pins during the assembly, due to the outward spring bias of the retaining ring 8. Experience has shown that it suffices to use only two threaded pins for the assembly or disassembly and for clearing.

What is claimed is:

1. A sewing machine hook comprising a body, and a bobbin case disposed in the body, said body defining a radially disposed circular track, said bobbin case having a generally radial flange including a surface cooperating with said track, an elastic, split retaining ring spaced from said track and limiting movement of said surface of the flange axially from said track, a plurality of screw-threaded elements disposed in corresponding ones of angularly spaced screw-threaded openings extending radially through the body, radially inner ends of said elements being tapered and contacting said ring to be constituted as means, upon adjustment of the radial position of the elements within the screw-threaded openings, for varying the axial spacing of said ring from said track.

2. A sewing machine hook as claimed in I wherein said ring is of circular section.

3. A sewing machine hook as claimed in claim 2, wherein an end portion of said ring is bent radially outwardly and is received in a slot formed in said body.

4. A sewing machine hook as claimed in claim 2, wherein an end portion of said ring is tapered to a point, said point being disposed on an outside diameter of said ring. 7

5. A sewing machine hook as claimed in claim 1, wherein said body includes an annular surface inclined towards said track, said ring being disposed between said inclined surface and said screw-threaded elements, adjustment of said screw-elements radially inwards of said body causing said ring to be moved inwardly along said inclined surface toward said track.

6. A sewing machine hook as claimed in claim 1, wherein said flange of said bobbin case has on a side thereof opposite to the surface cooperating with said track, a surface inclined toward said track of said body, said ring being disposed between said screw threaded elements and said inclined surface of the flange and contacting that inclined surface, adjustment of said screw-threaded elements radially inwards causing said ring to move along said inclined surface toward said track.

7. A sewing machine hook as claimed in claim 1, wherein said body includes an annular surface inclined toward said track and said flange of said case has on a side thereof opposite to the surface cooperating with said track, a surface inclined towards said track, said ring contacting said inclined surface of said body and said inclined surface of said case, adjustment of said screw-threaded elements inwardly of said openings producing radial and axial adjustment of said bobbin case relative to said track.

8. A sewing machine hook as claimed in claim 3, wherein said slot is of oblong outline having a major axis disposed axially of said body. 

1. A sewing machine hook comprising a body, and a bobbin case disposed in the body, said body defining a radially disposed circular track, said bobbin case having a generally radial flange including a surface cooperating with said track, an elastic, split retaining ring spaced from said track and limiting movement of said surface of the flange axially from said track, a plurality of screw-threaded elements disposed in corresponding ones of angularly spaced screw-threaded openings extending radially through the body, radially inner ends of said elements being tapered and contacting said ring to be constituted as means, upon adjustment of the radial position of the elements within the screw-threaded openings, for varying the axial spacing of said ring from said track.
 2. A sewing machine hook as claimed in 1 wherein said ring is of circular section.
 3. A sewing machine hook as claimed in claim 2, wherein an end portion of said ring is bent radially outwardly and is received in a slot formed in said body.
 4. A sewing machine hook as claimed in claim 2, wherein an end portion of said ring is tapered to a point, said point being disposed on an outside diameter of said ring.
 5. A sewing machine hook as claimed in claim 1, wherein said body includes an annular surface inclined towards said track, said ring being disposed between said inclined surface and said screw-threaded elements, adjustment of said screw-elements radially inwards of said body causing said ring to be moved inwardly along said inclined surface toward said track.
 6. A sewing machine hook as claimed in claim 1, wherein said flange of said bobbin case has on a side thereof opposite to the surface cooperating with said track, a surface inclined toward said track of said body, said ring being dIsposed between said screw-threaded elements and said inclined surface of the flange and contacting that inclined surface, adjustment of said screw-threaded elements radially inwards causing said ring to move along said inclined surface toward said track.
 7. A sewing machine hook as claimed in claim 1, wherein said body includes an annular surface inclined toward said track and said flange of said case has on a side thereof opposite to the surface cooperating with said track, a surface inclined towards said track, said ring contacting said inclined surface of said body and said inclined surface of said case, adjustment of said screw-threaded elements inwardly of said openings producing radial and axial adjustment of said bobbin case relative to said track.
 8. A sewing machine hook as claimed in claim 3, wherein said slot is of oblong outline having a major axis disposed axially of said body. 